Arsenic-induced suicidal erythrocyte death

Hemocompatibility studies in nanotoxicology: Hemolysis or eryptosis? (A review)

Hemocompatibility evaluation is an important step in nanotoxicological studies. It is generally accepted that nanomaterials promote lysis of erythrocytes, blood clotting, alter phagocytosis, and upregulate pro-inflammatory cytokines. However, there are no standardized guidelines for testing nanomaterials hemocompatibility despite the fact that nanomaterials enter the bloodstream and interact with blood cells. In this review, the current knowledge on the ability of nanomaterials to induce distinct cell death modalities of erythrocytes is highlighted primarily focusing on hemolysis and eryptosis. This review aims to summarize the molecular mechanisms underlying erythrotoxicity of nanomaterials and critically compare the sensitivity and efficiency of hemolysis or eryptosis assays for nanomaterials blood compatibility testing. The list of eryptosis-inducing nanomaterials is growing, but it is still difficult to generalize how physico-chemical properties of nanoparticles affect eryptosis degree and molecular mechanisms involved. Thus, another aim of this review is to raise the awareness of eryptosis as a nanotoxicological tool to encourage the corresponding studies. It is worthwhile to consider adding eryptosis to in vitro nanomaterials hemocompatibility testing protocols and guidelines.

Research progress on arsenic, arsenic-containing medicinal materials, and arsenic-containing preparations: clinical application, pharmacological effects, and toxicity

Introduction: The toxicity of arsenic is widely recognized globally, mainly harming human health by polluting water, soil, and food. However, its formulations can also be used for the clinical treatment of diseases such as leukemia and tumors. Arsenic has been used as a drug in China for over 2,400 years, with examples such as the arsenic-containing drug realgar mentioned in Shennong's Herbal Classic. We have reviewed references on arsenic over the past thirty years and found that research has mainly focused on clinical, pharmacological, and toxicological aspects. Results and Discussion: The finding showed that in clinical practice, arsenic trioxide is mainly used in combination with all-trans retinoic acid (ATRA) at a dose of 10 mg/d for the treatment of acute promyelocytic leukemia (APL); realgar can be used to treat acute promyelocytic leukemia, myelodysplastic syndrome, and lymphoma. In terms of pharmacology, arsenic mainly exerts anti-tumor effects. The dosage range of the action is 0.01-80 μmol/L, and the concentration of arsenic in most studies does not exceed 20 μmol/L. The pharmacological effects of realgar include antiviral activity, inhibition of overactivated lactate dehydrogenase, and resistance to malaria parasites. In terms of toxicity, arsenic is toxic to multiple systems in a dose-dependent manner. For example, 5 μmol/L sodium arsenite can induce liver oxidative damage and promote the expression of pro-inflammatory factors, and 15 μmol/L sodium arsenite induces myocardial injury; when the concentration is higher, it is more likely to cause toxic damage.

Arsenic exposure is associated with alterations to multiple red blood cell parameters among adults in rural Bangladesh

Chronic arsenic exposures are associated with multiple hematologic disturbances, including anemia. The goal of this study was to evaluate associations between arsenic exposures and hematological parameters among men and women who are chronically exposed to elevated levels of arsenic from drinking water. Hematologic analyses were performed on blood collected from 755 participants (45% male and 54% female) in the Health Effects of Arsenic Longitudinal Study (HEALS) cohort, Bangladesh. Herein, we used linear regression models to estimate associations between red blood cell (RBC) parameters (i.e., RBC counts, hematocrit (HCT), hemoglobin (Hgb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC)) and measurements of arsenic exposure (urinary arsenic and urinary arsenic metabolites). Arsenic exposures showed trending associations with decreased RBC counts in both men and women, a positive association with MCV in males, and an inverse association with MCHC among males, but not among non-smoking females. Among men, those who smoked had stronger associations between arsenic exposures and MCHC than non-smoking males. Collectively, our results show that arsenic exposures affect multiple RBC parameters and highlight potentially important sex differences in arsenic-induced hematotoxicity.

Geological context and human exposures to element mixtures in mining and agricultural settings in Colombia

Anthropogenic and natural sources contribute to chemical mixtures in air, water, and soil, posing potential risks to the environment and human health. To understand the interplay between element profiles in the human body, geographical location, and associated economic activities, we carried out an observational analytic cross-sectional study. The study recruited 199 participants from three municipalities, two of which had gold-mining as their primary economic activity, while the other was dedicated to agricultural and other local activities not related to mining. The concentrations of a total of 30 elements in human hair samples and 21 elements in environmental soil samples were measured using various spectrometry techniques. Unsupervised clustering analysis using Self-Organizing Maps was applied to human hair samples to analyze element concentrations. Distinct clusters of individuals were identified based on their hair element profiles, which were mapped to geographical location and economic activities. While higher levels of heavy metals (Ag, As, Hg, and Pb) were observed in individuals engaged in mining activities in certain clusters, individuals in agricultural areas show higher concentrations of elements found in pesticides (Ba and Sr). However, the elemental composition of hair is influenced not only by the anthropogenic activities but also by the inherent geological context where people live. Our findings highlight the significance of accounting for environmental factors when evaluating human health risks, as the intricate mixture of elements can yield valuable insights for targeted health interventions.

Casein kinase 1α mediates eryptosis: a review

Eryptosis is a coordinated non-lytic cell death of erythrocytes characterized by cell shrinkage, cell membrane scrambling, Ca²⁺ influx, ceramide accumulation, oxidative stress, activation of calpain and caspases. Physiologically, it aims at removing damaged or aged erythrocytes from circulation. A plethora of diseases are associated with enhanced eryptosis, including metabolic diseases, cardiovascular pathology, renal and hepatic diseases, hematological disorders, systemic autoimmune pathology, and cancer. This makes eryptosis and eryptosis-regulating signaling pathways a target for therapeutic interventions. This review highlights the eryptotic signaling machinery containing several protein kinases and its small molecular inhibitors with a special emphasis on casein kinase 1α (CK1α), a serine/threonine protein kinase with a broad spectrum of activity. In this review article, we provide a critical analysis of the regulatory role of CK1α in eryptosis, highlight triggers of CK1α-mediated suicidal death of red blood cells, cover the knowledge gaps in understanding CK1α-driven eryptosis and discover the opportunity of CK1α-targeted pharmacological modulation of eryptosis. Moreover, we discuss the directions of future research focusing on uncovering crosstalks between CK1α and other eryptosis-regulating kinases and pathways.

Protective Effect of Lactobacillus sporogenes against Arsenic-Induced Hematological Alterations in Male Albino Wistar Rats

The aim of the present study was to evaluate the arsenic-induced hemotoxicity and to evaluate the protective effects of Lactobacillus sporogenes in male albino Wistar rats. A total of 36 adult male albino Wistar rats were procured and divided into 3 groups of 12 animals each. Group 1 rats served as control, group 2 rats were administered sodium arsenite (@5 mg/kg BW/day), groups 3 rats were supplemented with L. sporogenes (@15 million spores/kg BW/day) along with sodium arsenite administered along with sodium arsenite orally daily for 28 consecutive days. Weekly body weights, hematological profile, and erythrocyte morphology were assessed. Significant (P < 0.05) reduction in mean weekly body weights (g) was observed in group 2 than group 1; however, a significant (P < 0.05) increase in weekly body weights was observed in group 3 as compared to group 2. A significant (P < 0.05) decrease in erythrocyte-related parameters and platelet counts, and a significant (P < 0.05) leukocytosis, relative lymphopenia, absolute neutrophilia, and monocytosis were noticed among arsenic-treated rats when compared to the control group. Blood smear of arsenic-treated rats contains echinocytes, microcytes, and spherocytes when compared to control. Scanning electron microscopic examination of blood revealed altered erythrocyte morphology in arsenic-treated rats with poikilocytosis and blebbing of the erythrocyte membrane. Supplementation of L. sporogenes along with arsenic resulted in improvement of all the hematological parameters and reduction in morphological abnormalities in comparison to the toxic control group. It is concluded that supplementation of L. sporogenes can effectively alleviate the arsenic-induced hematological alterations.

Arsenic retention in erythrocytes and excessive erythrophagocytosis is related to low selenium status by impaired redox homeostasis

Arsenic (As) contamination in drinking water is a global public health problem. Epidemiological studies have shown that selenium (Se) deficiency is associated with an increasing risk of arsenism. However, the association between Se status and As retention in erythrocytes and mechanisms underlying this association have not been fully investigated. In the present study, a total of 165 eligible subjects were recruited and As was found to accumulate in blood mainly by retention in erythrocytes. Retention of As in erythrocytes was negatively correlated with Se status, antioxidant parameters related to Se and As methylation capacity, but positively correlated with the protein-binding capacity of As. Additionally, erythrocytes isolated from subjects with low Se status exhibited cellular damage along with lower protein levels of CD47, which could be aggravated by hydrogen peroxide treatment. Consistent with the human study, the erythrocytes from mice with sub-chronic As exposure exhibited similar cellular damage and shown to be phagocytosed by splenic macrophages, and these effects were mitigated by dietary Se supplementation. Furthermore, hydrogen peroxide treatment induced excessive phagocytosis of erythrocytes with As exposure by splenic macrophages, while co-treating erythrocytes with the reducing agent, N-Acetyl-l-cysteine, mitigated this excessive erythrophagocytosis. Hyperactivation of the NFκB pathway was also detected in splenic macrophages after excessive erythrophagocytosis. In conclusion, this study found that low Se status involving impaired redox homeostasis increased As retention in erythrocytes, which were subsequently phagocytosed by splenic macrophages and led to an increased inflammatory status of splenic macrophages. These findings provide insight into physiological features of arsenism related to Se status and redox homeostasis.

Factors associated with anaemia in a nationally representative sample of nonpregnant women of reproductive age in Nepal

We used cross-sectional data from the 2016 Nepal National Micronutrient Status Survey to evaluate factors associated with anaemia among a nationally representative sample of nonpregnant women 15- 49 years (n = 1, 918). Haemoglobin, biomarkers of iron status and other micronutrients, infection, inflammation, and blood disorders were assessed from venous blood. Soil-transmitted helminth and Helicobacter pylori infections were assessed from stool. Sociodemographic, household, and health characteristics and diet were ascertained by interview. We conducted bivariate analyses between candidate predictors and anaemia (haemoglobin <12.0 g/ dL, altitude- and smoking-adjusted). Candidate predictors that were significant in bivariate models (P < 0.05) were included in the multivariable logistic regression model, accounting for complex sampling design. Anaemia prevalence was 20.2% (95% confidence interval [CI] [17.6, 22.8]). Associated with reduced anaemia odds were living in the Mountain and Hill ecological zones relative to the Terai (adjusted odds ratio [AOR] 0.35, 95% CI [0.21, 0.60] and AOR 0.41, 95% CI [0.29, 0.59], respectively), recent cough (AOR 0.56, 95% CI [0.38, 0.82]), hormonal contraceptive use (AOR 0.58; 95% CI [0.38, 0.88]), ln ferritin (micrograms per litre; AOR 0.43, 95% CI [0.35, 0.54]), and ln retinol binding protein (micrograms per litre; AOR 0.20, 95% CI [0.11, 0.37]). Residing in a house with an earth floor (AOR 1.74, 95% CI [1.18, 2.56]), glucose-6- phosphate dehydrogenase deficiency (AOR 2.44, 95% CI [1.66, 3.60]), and haemoglobinopathies (AOR 6.15, 95% CI [3.09, 12.26]) were associated with increased anaemia odds. Interventions that improve micronutrient status, ensure access to hormonal birth control, and replace dirt floors to reduce infection risk might help reduce anaemia in this population.

Arsenic exposure and non-carcinogenic health effects

Inorganic arsenic (iAs) exposure is a serious health problem that affects more than 140 million individuals worldwide, mainly, through contaminated drinking water. Acute iAs poisoning produces several symptoms such as nausea, vomiting, abdominal pain, and severe diarrhea, whereas prolonged iAs exposure increased the risk of several malignant disorders such as lung, urinary tract, and skin tumors. Another sensitive endpoint less described of chronic iAs exposure are the non-malignant health effects in hepatic, endocrine, renal, neurological, hematological, immune, and cardiovascular systems. The present review outlines epidemiology evidence and possible molecular mechanisms associated with iAs-toxicity in several non-carcinogenic disorders.

Factors affecting anaemia among women of reproductive age in Nepal: a multilevel and spatial analysis

OBJECTIVE

The main objective of this study was to explore the factors affecting anaemia among women of reproductive age (WRA) in Nepal using spatial and multilevel epidemiological analysis.

DESIGN

This cross-sectional study analysed data from the 2016 Nepal Demographic and Health Survey. Spatial analysis was performed using ArcGIS software V.10.8 to identify the hot and cold spots of anaemia among WRA (15-49 years). Data were analysed using multilevel mixed-effect logistic regression analysis.

SETTING

Nepal.

PARTICIPANTS

A total of 6414 WRA were included in the analysis.

MAIN OUTCOME MEASURE

Anaemia defined by WHO as haemoglobin level less than 120 g/L in non-pregnant women and less than 110 g/L in pregnant women.

RESULTS

The spatial analysis showed that statistically significant hotspots of anaemia were in the southern Terai region (four districts in province 1, eight districts in province 2, one district in Bagmati province, two districts in province 5 and one district in Sudurpaschim province) of Nepal. At the individual level, women who underwent female sterilisation (adjusted OR, aOR: 3.61, 95% CI 1.10 to 11.84), with no education (aOR: 1.99, 95% CI: 1.17 to 3.39), and from middle socioeconomic class families (aOR: 1.65, 95% CI: 1.02 to 2.68) were more likely to be anaemic, whereas, older women (>35 years) (aOR: 0.51, 95% CI: 0.26 to 0.97) and those women who were using hormonal contraceptives (aOR: 0.63, 95% CI: 0.43 to 0.90) were less likely to be anaemic. At the community level, women from province 2 (aOR=2.97, 95% CI: 1.52 to 5.82) had higher odds of being anaemic.

CONCLUSION

WRA had higher odds of developing anaemia, and it varied by the geographical regions. Nutrition-specific and nutrition-sensitive interventions can be tailored based on the factors identified in this study to curb the high burden of anaemia.

Experimental acute arsenic toxicity in Balb/c mice: organic markers and splenic involvement

Introduction: Arsenic is an environmental toxic present worldwide. In men and animals, various organs and tissues are targets of its deleterious effects including those of the immune system. Objective: To determine acute arsenic toxicity in tissues and target cells of Balb/c mice using an in vivo methodology. Materials and methods: We injected Balb/c mice intraperitoneally with 9.5 or 19 mg/kg of sodium arsenite (NaAsO2), or an equivalent volume of physiological solution as a control (with 3 per experimental group). After 30 minutes, the animals were sacrificed to obtain spleen, thymus, liver, kidneys, and blood. We determined arsenic, polyphenols, and iron concentrations in each sample and we evaluated the oxidative markers (peroxides, advanced products of protein oxidation, and free sulfhydryl groups). In splenocytes from the spleen, cell viability and mitochondrial potential were also determined. Results: The exposure to an acute dose of NaAsO2 reduced the mitochondrial function of splenocytes, which resulted in cell death. Simultaneously, the confirmed presence of arsenic in spleen samples and the resulting cytotoxicity occurred with a decrease in polyphenols, free sulfhydryl groups, and an alteration in the content and distribution of iron, but did not increase the production of peroxides. Conclusion: These findings provide scientific evidence about changes occurring in biomarkers involved in the immunotoxicity of arsenic and offer a methodology for testing possible treatments against the deleterious action of this compound on the immune system.

Erythrocytes as model cells for biocompatibility assessment, cytotoxicity screening of xenobiotics and drug delivery

Erythrocytes (RBCs) represent the main cell component in circulation and recently have become a topic of intensive scientific interest. The relevance of erythrocytes as a model for cytotoxicity screening of xenobiotics is under the spotlight of this review. Erythrocytes constitute a fundamental cellular model to study potential interactions with blood components of manifold novel polymer or biomaterials. Morphological changes, subsequent disruption of RBC membrane integrity, and hemolysis could be used to determine the cytotoxicity of various compounds. Erythrocytes undergo a programmed death (eryptosis) which could serve as a good model for evaluating certain mechanisms which correspond to apoptosis taking place in nucleated cells. Importantly, erythrocytes can be successfully used as a valuable cellular model in examination of oxidative stress generated by certain diseases or multiple xenobiotics since red cells are subjected to permanent oxidative stress. Additionally, the antioxidant capacity of erythrocytes, and the activity of anti-oxidative enzymes could reflect reactive oxygen species (ROS) generating properties of various substances and allow to determine their effects on tissues. The last part of this review presents the latest findings on the possible application of RBCs as drug delivery systems (DDS). In conclusion, all these findings make erythrocytes highly valuable cells for in vitro biocompatibility assessment, cytotoxicity screening of a wide variety of substances as well as drug delivery.

Arsenic, Cadmium and Lead Erythrocyte Concentrations in Men with a High, Moderate and Low Level of Physical Training

The aim of the present study was to determine changes occurring in the erythrocyte concentrations of arsenic (As), cadmium (Cd) and lead (Pb) in highly trained males, moderately trained males and sedentary men living in the same area of Extremadura (Spain). Thirty sedentary subjects (24.34 ± 3.02 years) with no sports practice and a less active lifestyle formed the control group (CG). Twenty-four moderately trained subjects (23.53 ± 1.85 years), who practised sports at a moderate level between 4 and 7 h/week, without any performance objective and without following any type of systematic training, formed the group of subjects with a moderate degree of training (MTG). And 22 professional cyclists (23.29 ± 2.73 years) at the beginning of their sports season, who trained for more than 20 h/week formed the high-level training group (HTG). Erythrocyte samples from all subjects in a fasting stage were collected, washed and frozen at -80 °C until analysis. Erythrocyte analysis of the trace elements As, Cd and Pb was performed by inductively coupled plasma mass spectrometry (ICP-MS). As concentration was lower in CG (p < 0.01) and MTG (p < 0.01) than HTG. Cd (p < 0.001) and Pb (p < 0.05) concentrations were higher in CG than HTG. All results were expressed in μg/g Hb. Physical training produces a decrease in erythrocyte concentrations of Cd and Pb, as an adaptation in order to avoid their accumulation in the cells and preserve correct cellular functioning. The higher As concentration should be investigated in high-level sportsmen because of a possible negative effect on the cells.

Factors associated with anaemia among adolescent boys and girls 10-19 years old in Nepal

We used data from the 2016 Nepal National Micronutrient Status Survey to evaluate factors associated with anaemia (World Health Organization cut-points using altitude- and smoking-adjusted haemoglobin [Hb]) among nationally representative samples of adolescents 10-19 years. Hb, biomarkers of micronutrients, infection and inflammation were assessed from venous blood. Sociodemographic and household characteristics, dietary diversity, pica and recent morbidity were ascertained by interview. We explored bivariate relationships between candidate predictors and anaemia among boys (N = 967) and girls (N = 1,680). Candidate predictors with P < 0.05 in bivariate analyses were included in sex-specific multivariable logistic regression models. Anaemia prevalence was 20.6% (95% confidence interval [CI] [17.1, 24.1]) among girls and 10.9% (95% CI [8.2, 13.6]) among boys. Among girls, living in the Mountain and Hill ecological zones relative to the Terai (adjusted odds ratio [AOR] 0.28, 95% CI [0.15, 0.52] and AOR 0.42, 95% CI [0.25, 0.73], respectively), ln ferritin (μg/L) (AOR 0.53, 95% CI [0.42, 0.68]) and ln retinol binding protein (RBP) (μmol/L) (AOR 0.08, 95% CI [0.04, 0.16]) were associated with reduced anaemia odds. Older age (age in years AOR 1.19, 95% CI [1.12, 1.27]) and Janajati ethnicity relative to the Muslim ethnicity (AOR 3.04, 95% CI [1.10, 8.36]) were associated with higher anaemia odds. Among boys, ln RBP [μmol/L] (AOR 0.25, 95% CI [0.10, 0.65]) and having consumed flesh foods (AOR 0.57, 95% CI [0.33, 0.99]) were associated with lower anaemia odds. Open defecation (AOR 2.36, 95% CI [1.15, 4.84]) and ln transferrin receptor [mg/L] (AOR 3.21, 95% CI [1.25, 8.23]) were associated with increased anaemia odds. Anaemia among adolescents might be addressed through effective public health policy and programs targeting micronutrient status, diet and sanitation.

Gallic acid and MiADMSA reversed arsenic induced oxidative/nitrosative damage in rat red blood cells

Arsenic (As) is naturally occurring toxic metalloid which is considered as a serious environmental and health concern. Red blood cells are the prime target for any toxicants as their population is higher in systemic circulation. High prevalence of anaemia too has been reported from arsenic contaminated area, suggesting possible linkage between arsenic and the damaging effects on RBCs. The exact mechanism for these effects is still not clear, however, oxidative/nitrosative stress might be one of the causative factors to play a key role. The present study was planned to evaluate the protective effects of a metal chelator, MiADMSA either alone or in combination with a natural antioxidant (gallic acid) for the reversal of arsenic induced oxidative damage in red blood cells. We collected rat RBCs and cultured them in appropriate medium. They were incubated with MiADMSA and gallic acid and then treated with sodium arsenite at 37 °C. Hemolysates were prepared and assayed for various biochemical parameters such as oxidative/nitrosative variables, osmotic fragility, acetylcholinesterase activity, and cellular metal accumulation. We found there was reversibility of oxidative/nitrosative stress variables, elevated cellular antioxidant power, and decreased osmotic fragility of red blood cells both in MiADMSA alone as well as in combination with gallic acid treated group compared with arsenic treated group. In conclusion, MiADMSA efficiently participated in the reversal of arsenic induced oxidative/nitrosative damage in red blood cells where as Gallic acid improved its reversal when given in combination with MiADMSA.

The second generation tyrosine kinase inhibitor dasatinib induced eryptosis in human erythrocytes-An in vitro study

Dasatinib, a new tyrosine kinase inhibitor, is used clinically to kill chronic myelogenous leukemia and acute lymphoblastic leukemia through apoptosis. Obviously, anemia is developed in many patients receiving dasatinib for treatment. Until now, the mechanism for the cytotoxic effects of dasatinib in human erythrocytes is not fully understood. As many tyrosine kinases are found in human erythrocytes, it is therefore logical to hypothesize that dasatinib is able to induce apoptosis (or eryptosis) in human erythrocytes. True to our expectation, dasatinib inhibited tyrosine kinase and induced eryptosis in human erythrocytes with early denature of esterase, cell shrinkage, loss of membrane integrity with inside-out phosphatidylserine, increase in the cytosolic Ca²⁺ ion concentration ([Ca²⁺]i), caspase-3 activation and change in cellular redox state. Mechanistically, the rise of [Ca²⁺]i seems to be a key mediator in the dasatinib-mediated eryptosis because depletion of external Ca²⁺ could suppress the eryptotic effects. Also, dasatinib was able to reduce membrane fluidity in human RBCs. For the direct action on membrane, dasatinib permeabilized RBC ghosts in a way similar to digitonin. Taken together, we report here for the first time that dasatinib inhibited tyrosine kinase and induced eryptosis in human erythrocytes through Ca²⁺ loading and membrane permeabilization.

Eryptosis: An Erythrocyte's Suicidal Type of Cell Death

Erythrocytes play an important role in oxygen and carbon dioxide transport. Although erythrocytes possess no nucleus or mitochondria, they fulfil several metabolic activities namely, the Embden-Meyerhof pathway, as well as the hexose monophosphate shunt. Metabolic processes within the erythrocyte contribute to the morphology/shape of the cell and important constituents are being kept in an active, reduced form. Erythrocytes undergo a form of suicidal cell death called eryptosis. Eryptosis results from a wide variety of contributors including hyperosmolarity, oxidative stress, and exposure to xenobiotics. Eryptosis occurs before the erythrocyte has had a chance to be naturally removed from the circulation after its 120-day lifespan and is characterised by the presence of membrane blebbing, cell shrinkage, and phosphatidylserine exposure that correspond to nucleated cell apoptotic characteristics. After eryptosis is triggered there is an increase in cytosolic calcium (Ca2+) ion levels. This increase causes activation of Ca2+-sensitive potassium (K+) channels which leads to a decrease in intracellular potassium chloride (KCl) and shrinkage of the erythrocyte. Ceramide, produced by sphingomyelinase from the cell membrane's sphingomyelin, contributes to the occurrence of eryptosis. Eryptosis ensures healthy erythrocyte quantity in circulation whereas excessive eryptosis may set an environment for the clinical presence of pathophysiological conditions including anaemia.

Arsenic exposures alter clinical indicators of anemia in a male population of smokers and non-smokers in Bangladesh

Drinking water arsenic (WAs) exposure has been linked to a number of detrimental health outcomes including anemia, primarily among pregnant women. Little is known about the effects of arsenic (As) on hematological disorders among men. We have examined the role of As exposure on hematological indicators of anemia in a group of men exposed to a wide range of As in their drinking water. We conducted a cross-sectional investigation among 119 healthy men in the Health Effects of As Longitudinal Study (HEALS) cohort, in rural Bangladesh. The participants are part of an ongoing study focused on evaluating the influence of As and smoking on immune function. Samples were collected at recruitment and analyzed for water As, urinary As (UAs) and UAs metabolites to assess As exposure. Blood samples were also collected at recruitment and assayed immediately for hematological parameters. We found that increased WAs levels were associated with decreased red blood cell counts [β=-0.13, p<0.0001] as well as hematocrit packed cell volumes [β=-0.68, p=0.008] following adjustment for age, smoking, body mass index and polycyclic aromatic hydrocarbon-DNA adducts. Other measures of As exposure (UAs and its metabolites) demonstrated similar associations. Slightly stronger effects were observed among smokers. We also observed an effect of As on hemoglobin among smokers in relation to UAs [β=-0.54, p<0.05]. Our analysis revealed effects of As exposure on hematological indicators of anemia in a group of healthy male smokers and non-smokers.

α-Lipoic Acid Mitigates Arsenic-Induced Hematological Abnormalities in Adult Male Rats

BACKGROUND

Arsenic toxicity is a major global health problem and exposure via contaminated drinking water has been associated with hematological and other systemic disorders. The present investigation has been conducted in adult male rats to evaluate the protective ability of α-lipoic acid (ALA) against such hematological disorders.

METHODS

Twenty-four adult male Wister rats (b.wt.130±10g) were grouped and accordingly group I (control) received the normal diet, group II (treated) was given arsenic orally for 28 consecutive days as arsenic trioxide (3 mg/kgbw/rat/day) whereas group III (supplemented) received the same dose of arsenic along with ALA (25 mg/kgbw/rat/day) as oral supplement. Hematological profile, plasma oxidant/antioxidant status, and erythrocyte morphology were assessed. Statistical analysis was done by one-way ANOVA using SPSS software (version 16.0).

RESULTS

Arsenic exposure caused reduction of erythrocyte (P=0.021), leucocyte (P<0.001), and hemoglobin (P=0.031) associated with echinocytic transformation as evidenced by light and scanning electron microscopic studies. The other significantly altered parameters include increased mean corpuscular volume (P=0.041) and lymphocytopenia (P<0.001) with insignificant neutropenia and eosinophilia. Altered serum oxidative balance as evidenced by decreased TAS (P<0.001) and increased TOS (P<0.001) with OSI (P<0.001) was also noted. The dietary supplementation of ALA has a beneficial effect against the observed (P<0.05) arsenic toxicities. It brings about the protection by restoring the hematological redox and inflammatory status near normal in treated rats. Arsenic-induced morphological alteration of erythrocytes was also partially attenuated by ALA supplementation.

CONCLUSION

It is concluded that arsenicosis is associated with hematological alterations and ALA co-supplementation can partially alleviate these changes in an experimental male rat model.

Cytotoxicity and alterations at transcriptional level caused by metals on fish erythrocytes in vitro

The in vitro use of fish erythrocytes to test the toxicity of aquatic pollutants could be a valuable alternative to fish bioassays but has received little attention. In this study, erythrocytes from marine gilthead sea bream (Sparus aurata L.) and European sea bass (Dicentrarchus labrax L.) specimens were exposed for 24 h to Cd, Hg, Pb and As and the resulting cytotoxicity was evaluated. Exposure to metals produced a dose-dependent reduction in the viability, and mercury showed the highest toxicity followed by MeHg, Cd, As and Pb. Moreover, fish erythrocytes incubated with each one of the metals exhibited alteration in gene expression profile of metallothionein, superoxide dismutase, catalase, peroxiredoxin, glutathione reductase, heat shock proteins 70 and 90, Bcl2-associated X protein and calpain1 indicating cellular protection, stress and apoptosis death as well as oxidative stress. This study points to the benefits for evaluating the toxicological mechanisms of marine pollution using fish erythrocytes in vitro.

A cross sectional study of anemia and iron deficiency as risk factors for arsenic-induced skin lesions in Bangladeshi women

BACKGROUND

In the Ganges Delta, chronic arsenic poisoning is a health concern affecting millions of people who rely on groundwater as their potable water source. The prevalence of anemia is also high in this region, particularly among women. Moreover, arsenic is known to affect heme synthesis and erythrocytes and the risk of arsenic-induced skin lesions appears to differ by sex.

METHODS

We conducted a case-control study in 147 arsenic-exposed Bangladeshi women to assess the association between anemia and arsenic-induced skin lesions.

RESULTS

We observed that the odds of arsenic-related skin lesions were approximately three times higher among women who were anemic (hemoglobin < 120 g/L) compared to women with normal hemoglobin levels [Odds Ratio (OR) = 3.32, 95% Confidence Intervals (CI): 1.29, 8.52] after adjusting for arsenic levels in drinking water and other covariates. Furthermore, 75% of the women with anemia had adequate iron stores (serum ferritin ≥ 12 μg/L), suggesting that the majority of anemia detected in this population was unrelated to iron depletion.

CONCLUSIONS

Considering the magnitude of arsenic exposure and prevalence of anemia in Bangladeshi women, additional research is warranted that identifies the causes of anemia so that effective interventions can be implemented while arsenic remediation efforts continue.

Ceramide in the regulation of eryptosis, the suicidal erythrocyte death

Similar to apoptosis of nucleated cells, erythrocytes may undergo eryptosis, a suicidal death characterized by cell shrinkage and phospholipid scrambling of the cell membrane leading to phosphatidylserine exposure at the cell surface. As eryptotic erythrocytes are rapidly cleared from circulating blood, excessive eryptosis may lead to anemia. Moreover, eryptotic erythrocytes may adhere to the vascular wall and thus impede microcirculation. Stimulators of eryptosis include osmotic shock, oxidative stress and energy depletion. Mechanisms involved in the stimulation eryptosis include ceramide formation which may result from phospholipase A2 dependent formation of platelet activating factor (PAF) with PAF dependent stimulation of sphingomyelinases. Enhanced erythrocytic ceramide formation is observed in fever, sepsis, HUS, uremia, hepatic failure, and Wilson's disease. Enhanced eryptosis is further observed in iron deficiency, phosphate depletion, dehydration, malignancy, malaria, sickle-cell anemia, beta-thalassemia and glucose-6-phosphate dehydrogenase-deficiency. Moreover, eryptosis is triggered by osmotic shock and a wide variety of xenobiotics, which are again partially effective by enhancing ceramide abundance. Ceramide formation is inhibited by high concentrations of urea. As shown in Wilson's disease, pharmacological interference with ceramide formation may be a therapeutic option in the treatment of eryptosis inducing clinical disorders.

Triggers, inhibitors, mechanisms, and significance of eryptosis: the suicidal erythrocyte death

Suicidal erythrocyte death or eryptosis is characterized by erythrocyte shrinkage, cell membrane blebbing, and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Triggers of eryptosis include Ca(2+) entry, ceramide formation, stimulation of caspases, calpain activation, energy depletion, oxidative stress, and dysregulation of several kinases. Eryptosis is triggered by a wide variety of xenobiotics. It is inhibited by several xenobiotics and endogenous molecules including NO and erythropoietin. The susceptibility of erythrocytes to eryptosis increases with erythrocyte age. Phosphatidylserine exposing erythrocytes adhere to the vascular wall by binding to endothelial CXC-Motiv-Chemokin-16/Scavenger-receptor for phosphatidylserine and oxidized low density lipoprotein (CXCL16). Phosphatidylserine exposing erythrocytes are further engulfed by phagocytosing cells and are thus rapidly cleared from circulating blood. Eryptosis eliminates infected or defective erythrocytes thus counteracting parasitemia in malaria and preventing detrimental hemolysis of defective cells. Excessive eryptosis, however, may lead to anemia and may interfere with microcirculation. Enhanced eryptosis contributes to the pathophysiology of several clinical disorders including metabolic syndrome and diabetes, malignancy, cardiac and renal insufficiency, hemolytic uremic syndrome, sepsis, mycoplasma infection, malaria, iron deficiency, sickle cell anemia, thalassemia, glucose 6-phosphate dehydrogenase deficiency, and Wilson's disease. Facilitating or inhibiting eryptosis may be a therapeutic option in those disorders.

Mitochondrial toxin betulinic acid induces in vitro eryptosis in human red blood cells through membrane permeabilization

Betulinic acid (BA), a compound isolated from the bark of white birch (Betula pubescens), was reported to induce apoptosis in many types of cancer through mitochondrial dysfunction with low side effects in normal cells. Because of these features, BA is regarded as a potential anti-cancer agent. However, the effect of BA on the induction of cell death in human erythrocytes remains unknown. Given that BA is a mitochondrial toxin and mitochondria are the central cell death regulator, we hypothesized that BA is unable to elicit apoptosis (also known as eryptosis or erythroptosis) in human erythrocytes devoid of mitochondria. This study therefore tried to determine the in vitro effect of BA on the induction of eryptosis/erythroptosis. Contrary to our prediction, BA caused phosphatidylserine externalization, increase in cellular Ca(2+) ion concentration ([Ca(2+)]i) and eryptosis/erythroptosis in human erythrocytes with a lethal dose larger than that in cancer lines. Mechanistically, the rise of [Ca(2+)]i seems not to be the only key mediator in the BA-mediated eryptosis/erythroptosis because depletion of external Ca(2+) and use of Ca(2+) channels blockers could not eliminate the BA's effect. Also, BA was able to elicit discocyte-echinocyte transformation and release calcein from the RBC ghosts in a way similar to digitonin through membrane permeabilization. Collectively, we report here for the first time that BA induced eryptosis/erythroptosis in human erythrocytes through Ca(2+) loading and membrane permeabilization.

Ferutinin induces in vitro eryptosis/erythroptosis in human erythrocytes through membrane permeabilization and calcium influx

Ferutinin, isolated from the root of Ferula hermonis and proposed to be used as an antiosteoporosis phytoestrogen, has death promoting activities in a number of cancer cells. However, the effect of ferutinin on the induction of apoptosis in human red blood cells (RBCs), also known as eryptosis or erythroptosis, remains unclear. Given that ferutinin is a small molecule that can induce apoptosis in the cancer cells by opening the mitochondrial permeability transition pores, we therefore hypothesized that the effect of ferutinin to elicit apoptosis in human RBCs devoid of mitochondria would be minimal. This study tried to determine the in vitro effect of ferutinin on the induction of apoptosis in human RBCs. Eryptosis/erythroptosis after ferutinin treatment was examined for phosphatidylserine (PS) externalization, calcein leakage, and other apoptotic feature events by flow cytometry and confocal microscopy. Contrary to our prediction, ferutinin caused eryptosis/erythroptosis in human RBCs and simultaneously increased caspase-3 activity and the cytosolic free Ca(2+) ion level ([Ca(2+)]i). Yet, Ca(2+) seems not to be the sole mediator in ferutinin-mediated eryptosis/erythroptosis because depletion of the external Ca(2+) could not eliminate the apoptotic effect from ferutinin. Subsequent replenishment of the external Ca(2+) was able to promote PS externalization, caspase-3 activation, and rise of [Ca(2+)]i. Also, ferutinin at high dose (40 μM or above) was able to permeabilize the membrane of RBC ghosts in a way similar to that of digitonin. At low dose, ferutinin activated the P- and L-type Ca(2+) channels as the ferutinin-mediated [Ca(2+)]i rise was suppressed by the P-type (ω-agatoxin IVA) and L-type (verapamil and diltiazem) Ca(2+) channel blockers. Taken together, we report here for the first time that ferutinin induces in vitro apoptosis in human RBCs. Mechanistically, eryptosis/erythroptosis is mediated by membrane permeabilization and upregulation of [Ca(2+)]i with the activation of caspase-3.

Osteoresorptive arsenic intoxication

A 47-year-old woman consulted her dermatologist complaining whole body dermatitis, urticaria and irritating bullous eruptions on the plantar and side surfaces of her feet. She had had multiple hypopigmented spots on her skin since her early adulthood. The patient was treated with topical medication without significant improvement of symptoms. One year later she suffered a myocardial infarction, accompanied by refractory anaemia. At the age of 49, a breast cancer was diagnosed and shortly thereafter her last menstruation occurred. At age 50years, upon complaint of weight loss despite normal food intake, Hashimoto thyroiditis with latent hyperthyroidism, vitamin D insufficiency with secondary hyperparathyroidism, and poikilocytic anaemia with anisochromia, hypochromia, anisocytosis, elliptocytes, drepanocytes, dacryocytes, acanthocytes, echinocytes, schizocytes, stomatocytes and target cells were diagnosed. The osteodensitometric and laboratory examinations revealed osteoporosis with sustained elevation of urinary Dipyridinolin-crosslinks (u-Dpd), and urinary arsenic (u-As) of 500μg/l (equivalent to 0.5 parts per million-ppm, 2.5μg/mg creatinine/dl, u-As: Phosphate of 26μg/mmol; the estimated bone As:P and As/kg body weight were 500μg/g and 11.3mg/kg, respectively). Thalassemia, immunoglobinopathy and iron deficiency were excluded. Supplementation with oral vitamin D and calcium, and antiresorptive therapy with intravenous zolendronate normalised the u-Dpd, significantly decreased the urinary arsenic concentration, and cured the anemia and the urticaria. A diagnosis of osteoresorptive arsenic intoxication (ORAI) was established.

Enhanced apoptotic death of erythrocytes induced by the mycotoxin ochratoxin A

BACKGROUND

The mycotoxin ochratoxin A, an agent responsible for endemic Balkan nephropathy is known to trigger apoptosis and thus being toxic to several organs including the kidney. The mechanisms involved in ochratoxin A induced apoptosis include oxidative stress. Sequelae of ochratoxin intoxication include anemia. Similar to apoptosis of nucleated cells, erythrocytes may undergo suicidal cell death or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling resulting in phosphatidylserine-exposure at the cell surface. Eryptosis could be triggered by Ca2+ -entry through oxidant sensitive unspecificcation channels increasing cytosolic Ca2+ activity ([Ca2+]i). The Ca2+ -sensitivity of cell membrane scrambling could be enhanced and eryptosis thus triggered by ceramide. The removal of suicidal erythrocytes may lead to anemia. Moreover, eryptotic erythrocytes could adhere to the vascular wall thus impeding microcirculation. The present study explored, whether ochratoxin A stimulates eryptosis.

METHODS

Fluo3-fluorescence was utilized to determine [Ca2+]i, forward scatter to estimate cell volume, annexin-V-binding to identify phosphatidylserine-exposing cells, fluorescent antibodies to detect ceramide formation and hemoglobin release to quantify hemolysis. Moreover, adhesion to human vascular endothelial cells (HUVEC) was determined utilizing a flow chamber.

RESULTS

A 48 h exposure to ochratoxin A was followed by significant increase of Fluo3-fluorescencei (≥ 2.5 µM), increase of ceramide abundance (10 µM), decrease of forward scatter (≥ 5 µM) and increase of annexin-V-binding (≥ 2.5 µM). Ochratoxin A exposure slightly but significantly enhanced hemolysis (10 µM). Ochratoxin (10 µM) enhanced erythrocyte adhesion to HUVEC. Removal of extracellular Ca2+ significantly blunted, but did not abrogate ochratoxin A-induced annexin V binding.

CONCLUSIONS

Ochratoxin A triggers suicidal erythrocyte death or eryptosis, an effect partially but not fully due to stimulation of Ca2+ -entry.

Stimulation of suicidal death of erythrocytes by rifampicin

The antibiotic rifampicin is widely used in the treatment of tuberculosis. Side effects of rifampicin include hemolytic anemia. Loss of circulating erythrocytes resembling hemolytic anemia could result from stimulation of eryptosis, the suicidal erythrocyte death characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine (PS) exposure at the cell surface. Stimulators of eryptosis include increase of cytosolic Ca(2+) activity ([Ca(2+)](i)) and formation of ceramide. The present study explored, whether and, if so, how rifampicin triggers eryptosis. To this end, [Ca(2+)](i) was estimated from Fluo3 fluorescence, cell volume from forward scatter in flow cytometry, PS exposure from annexin binding, ceramide formation from binding of fluorescent antibodies and hemolysis from hemoglobin release. As a result, a 48 h exposure to rifampicin (≥ 24 μg/ml) significantly increased Fluo3 fluorescence, ceramide abundance and annexin binding, and significantly decreased forward scatter. Rifampicin triggered slight, but significant hemolysis. Removal of extracellular Ca(2+) significantly blunted, but did not fully abolish rifampicin induced annexin binding. In conclusion, exposure of human erythrocytes to rifampicin is followed by suicidal erythrocyte death or eryptosis, an effect at least partially due to increase of cytosolic Ca(2+) concentration and stimulation of ceramide formation.

Enhanced suicidal erythrocyte death in mice carrying a loss-of-function mutation of the adenomatous polyposis coli gene

Loss-of-function mutations in human adenomatous polyposis coli (APC) lead to multiple colonic adenomatous polyps eventually resulting in colonic carcinoma. Similarly, heterozygous mice carrying defective APC (apc^Min/+) suffer from intestinal tumours. The animals further suffer from anaemia, which in theory could result from accelerated eryptosis, a suicidal erythrocyte death triggered by enhanced cytosolic Ca²⁺ activity and characterized by cell membrane scrambling and cell shrinkage. To explore, whether APC-deficiency enhances eryptosis, we estimated cell membrane scrambling from annexin V binding, cell size from forward scatter and cytosolic ATP utilizing luciferin–luciferase in isolated erythrocytes from apc^Min/+ mice and wild-type mice (apc^+/+). Clearance of circulating erythrocytes was estimated by carboxyfluorescein-diacetate-succinimidyl-ester labelling. As a result, apc^Min/+ mice were anaemic despite reticulocytosis. Cytosolic ATP was significantly lower and annexin V binding significantly higher in apc^Min/+ erythrocytes than in apc^+/+ erythrocytes. Glucose depletion enhanced annexin V binding, an effect significantly more pronounced in apc^Min/+ erythrocytes than in apc^+/+ erythrocytes. Extracellular Ca²⁺ removal or inhibition of Ca²⁺ entry with amiloride (1 mM) blunted the increase but did not abrogate the genotype differences of annexin V binding following glucose depletion. Stimulation of Ca²⁺-entry by treatment with Ca²⁺-ionophore ionomycin (10 μM) increased annexin V binding, an effect again significantly more pronounced in apc^Min/+ erythrocytes than in apc^+/+ erythrocytes. Following retrieval and injection into the circulation of the same mice, apc^Min/+ erythrocytes were more rapidly cleared from circulating blood than apc^+/+ erythrocytes. Most labelled erythrocytes were trapped in the spleen, which was significantly enlarged in apc^Min/+ mice. The observations point to accelerated eryptosis and subsequent clearance of apc^Min/+ erythrocytes, which contributes to or even accounts for the enhanced erythrocyte turnover, anaemia and splenomegaly in those mice.

Inhibitory effect of furosemide on non-selective voltage-independent cation channels in human erythrocytes

BACKGROUND

Furosemide, a loop diuretic inhibiting the renal tubular Na(+),K(+),2Cl(-) cotransporter, has been shown to decrease cytosolic Ca(2+) concentration ([Ca(2+)](i)) in platelets and erythrocytes. [Ca(2+)](i) in erythrocytes is a function of Ca(2+) permeable cation channels. Activation of those channels e.g. by energy depletion or oxidative stress leads to increase of [Ca(2+)](i), which in turn triggers eryptosis, a suicidal erythrocyte death characterized by cell membrane scrambling. The present study was performed to explore whether furosemide influences the cation channels and thus influences eryptosis.

METHODS

Cation channel activity was determined by whole-cell patch clamp, [Ca(2+)](i) utilizing Fluo3 fluorescence and annexin V binding to estimate cell membrane scrambling with phosphatidylserine exposure.

RESULTS

A 45 min exposure to furosemide (10 and 100 µM) slightly, but significantly decreased cation channel activity and [Ca(2+)](i) in human erythrocytes drawn from healthy individuals. ATP-depletion (> 3 hours, +37°C, 6 mM ionosine and 6 mM iodoacetic acid) enhanced the non-selective cation channel activity, increased [Ca(2+)](i) and triggered cell membrane scrambling, effects significantly blunted by furosemide (10 - 100 µM). Oxidative stress by exposure to tert-butylhydroperoxide (0.1 -1 mM) similarly enhanced the non-selective cation channels activity, increased [Ca(2+)](i) and triggered cell membrane scrambling, effects again significantly blunted by furosemide (10 - 100 µM).

CONCLUSIONS

The present study shows for the first time that the loop diuretic furosemide applied at micromolar concentrations (10 - 100 µM) inhibits non-selective cation channel activity in and eryptosis of human erythrocytes.

Enhanced erythrocyte membrane exposure of phosphatidylserine following sorafenib treatment: an in vivo and in vitro study

BACKGROUND

Sorafenib (Nexavar(®)), a polytyrosine kinase inhibitor, stimulates apoptosis and is thus widely used for chemotherapy in hepatocellular carcinoma (HCC). Hematological side effects of Nexavar(®) chemotherapy include anemia. Erythrocytes may undergo apoptosis-like suicidal death or eryptosis, which is characterized by cell shrinkage and phosphatidylserine-exposure at the cell surface. Signaling leading to eryptosis include increase in cytosolic Ca(2+)activity ([Ca(2+)](i)), formation of ceramide, ATP-depletion and oxidative stress. The present study explored, whether sorafenib triggers eryptosis in vitro and in vivo.

METHODS

[Ca(2+)](i )was estimated from Fluo3-fluorescence, cell volume from forward scatter, phosphatidylserine-exposure from annexin-V-binding, hemolysis from hemoglobin release, ceramide with antibody binding-dependent fluorescence, cytosolic ATP with a luciferin-luciferase-based assay, and oxidative stress from 2',7' dichlorodihydrofluorescein diacetate (DCFDA) fluorescence.

RESULTS

A 48 h exposure of erythrocytes to sorafenib (≥0.5 µM) significantly increased Fluo 3 fluorescence, decreased forward scatter, increased annexin-V-binding and triggered slight hemolysis (≥5 µM), but did not significantly modify ceramide abundance and cytosolic ATP. Sorafenib treatment significantly enhanced DCFDA-fluorescence and the reducing agents N-acetyl-L-cysteine and tiron significantly blunted sorafenib-induced phosphatidylserine exposure. Nexavar(®) chemotherapy in HCC patients significantly enhanced the number of phosphatidylserine-exposing erythrocytes.

CONCLUSIONS

The present observations disclose novel effects of sorafenib, i.e. stimulation of suicidal erythrocyte death or eryptosis, which may contribute to the pathogenesis of anemia in Nexavar(®)-based chemotherapy.

Hematological effects of arsenic in rats after subchronical exposure during pregnancy and lactation: the protective role of antioxidants

Free radicals production is involved in the toxicity of arsenic. The aim of this study was to determine whether biochemical changes occurred in the blood of arsenic-exposed pups during gestation and lactation, and additionally to investigate the potential beneficial role of the administration of certain antioxidants against arsenic exposure damage. Pregnant wistar rats received the following treatments as drinking water: (1) distilled water; (2) arsenic (50 mg/L); (3) antioxidants: zinc (20 mg/L)+vitamin C (2 g/L)+vitamin E (500 mg/L); (4) arsenic (50 mg/L)+antioxidants: zinc (20 mg/L)+vitamin C (2 g/L)+vitamin E (500 mg/L). We found a normocytic and normochromic anemia as well as a significant increase in hemolysis, TBARS production and catalase activity in the blood of arsenic intoxicated pups. Moreover, this metalloid produced a significant increase of serum cholesterol, triglicerids and urea levels whereas the proteins diminished. These effects were palliated in some extent by the coadministration of vitamins and zinc. Our findings suggest that administration of antioxidants during gestation and lactation could prevent some of the negative effects of arsenic.

Polyphyllin D induces apoptosis in human erythrocytes through Ca²⁺ rise and membrane permeabilization

Polyphyllin D (PD) is a potent anticancer agent isolated from a traditional medicinal herb Paris polyphylla that has been used in China for many years to treat cancer. PD is not a substrate of p-glycoprotein, and it can bypass the multi-drug resistance in cancer cell line R-HepG2. However, the effect of PD on the induction of cell death in human erythrocytes remains unknown. Given that PD is a small molecule that can depolarize the mitochondrial membrane potential and release apoptosis-inducing factor (AIF) in isolated mitochondria, we hypothesized that the apoptogenic effect of PD in human erythrocytes devoid of mitochondria would be minimal. This study therefore tried to evaluate the in vitro effect of PD on hemolysis and apoptosis in human erythrocytes. Apoptosis in human red blood cells (RBCs), also known as eryptosis or erythroptosis, after PD treatment was determined by flow cytometry and confocal microscopy for the phosphatidyl-serine externalization and other apoptosis feature events. False to our prediction, PD caused hemolysis and eryptosis/erythroptosis in human RBCs. Mechanistically, elevation in the cytosolic Ca²⁺ ion level seems to be a key but not the only mediator in the PD-mediated eryptosis/erythroptosis because depletion of the external Ca²⁺ could not eliminate the PD effect. Also, PD was able to permeabilize the membrane of RBC ghosts in a way similar to digitonin. Taken together, we report here for the first time the toxicity of PD in human RBCs as well as its underlying mechanism for the hemolysis and eryptosis/erythroptosis.

Apigenin-induced suicidal erythrocyte death

Apigenin, a flavone in fruits and vegetables, stimulates apoptosis and thus counteracts cancerogenesis. Erythrocytes may similarly undergo suicidal cell death or eryptosis, characterized by cell shrinkage and phosphatidylserine exposure at the cell surface. Triggers of eryptosis include increase of cytosolic Ca(2+) activity ([Ca(2+)](i)), ceramide formation and ATP depletion. The present study explored the effect of apigenin on eryptosis. [Ca(2+)](i) was estimated from Fluo3-fluorescence, cell volume from forward scatter, phosphatidylserine exposure from annexin V binding, hemolysis from hemoglobin release, ceramide utilizing antibodies, and cytosolic ATP with luciferin-luciferase. A 48 h exposure to apigenin significantly increased [Ca(2+)](i) (≥ 1 μM), increased ceramide formation (15 μM), decreased ATP concentration (15 μM), decreased forward scatter (≥ 1 μM), and increased annexin V binding (≥ 5 μM) but did not significantly modify hemolysis. The effect of 15 μM apigenin on annexin V binding was blunted by Ca(2+) removal. The present observations reveal novel effects of apigenin, i.e. stimulation of Ca(2+) entry, ceramide formation and ATP depletion in erythrocytes with subsequent triggering of suicidal erythrocyte death, paralleled by cell shrinkage and phosphatidylserine exposure.

p38 MAPK activation and function following osmotic shock of erythrocytes

p38 protein kinase is activated by hyperosmotic shock, participates in the regulation of cell volume sensitive transport and metabolism and is involved in the regulation of various physiological functions including cell proliferation and apoptosis. Similar to apoptosis of nucleated cells, erythrocytes may undergo suicidal death or eryptosis, which is paralleled by cell shrinkage and cell membrane scrambling with phosphatidylserine exposure at the cell surface. Triggers of eryptosis include hyperosmotic shock, which increases cytosolic Ca(2+) activity and ceramide formation. The present study explored whether p38 kinase is expressed in human erythrocytes, is activated by hyperosmotic shock and participates in the regulation of eryptosis. Western blotting was utilized to determine phosphorylation of p38 kinase, forward scatter to estimate cell volume, annexin V binding to depict phosphatidylserine exposure and Fluo3 fluorescence to estimate cytosolic Ca(2+) activity. As a result, erythrocytes express p38 kinase, which is phosphorylated upon osmotic shock (+550 mM sucrose). Osmotic shock decreased forward scatter, increased annexin V binding and increased Fluo3 fluorescence, all effects significantly blunted by the p38 kinase inhibitors SB203580 (2 μM) and p38 Inh III (1 μM). In conclusion, p38 kinase is expressed in erythrocytes and participates in the machinery triggering eryptosis following hyperosmotic shock.

Dicoumarol activates Ca2+-permeable cation channels triggering erythrocyte cell membrane scrambling

Dicoumarol, a widely used anticoagulant, may cause anemia, which may result from enhanced erythrocyte loss due to bleeding or due to accelerated erythrocyte death. Erythrocytes may undergo suicidal death or eryptosis, characterized by cell shrinkage and phospholipid scrambling of the cell membrane. Eryptosis may be triggered by increase of cytosolic Ca(2+)-activity ([Ca(2+)](i)). The present study explored, whether dicoumarol induces eryptosis. [Ca(2+)](i) was estimated from Fluo3-fluorescence, cation channel activity utilizing whole cell patch clamp, cell volume from forward scatter, phospholipid scrambling from annexin-V-binding, and hemolysis from haemoglobin release. Exposure of erythrocytes for 48 hours to dicoumarol (=10 μM) significantly increased [Ca(2+)](i), enhanced cation channel activity, decreased forward scatter, triggered annexin-V-binding and elicited hemolysis. Following exposure to 30 μM dicoumarol, annexin-V-binding affected approximately 15%, and hemolysis 2% of treated erythrocytes. The stimulation of annexin-V-binding by dicoumarol was abrogated in the nominal absence of Ca(2+). In conclusion, dicoumarol stimulates suicidal death of erythrocytes by stimulating Ca(2+) entry and subsequent triggering of Ca(2+) dependent cell membrane scrambling.

Hexavalent chromium-induced erythrocyte membrane phospholipid asymmetry

Hexavalent (VI) chromium is a global contaminant with cytotoxic activity. Chromium (VI) induces oxidative stress, inflammation, cell proliferation, malignant transformation and may trigger carcinogenesis and at the same time apoptosis. The toxic effects of chromium (VI) at least partially result from mitochondrial injury and DNA damage. Erythrocytes lack mitochondria and nuclei but may experience an apoptosis-like suicidal cell death, i.e. eryptosis, which is characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine exposure at the cell surface. Eryptosis may result from increase of cytosolic Ca(2+) activity, ATP depletion and/or ceramide formation. The present study explored, whether chromium (VI) triggers eryptosis. Fluo-3-fluorescence was employed to determine cytosolic Ca(2+)-concentration, forward scatter to estimate cell volume, binding of fluorescent annexin V to detect phosphatidylserine exposure, hemoglobin concentration in the supernatant to quantify hemolysis, luciferin-luciferase to determine cytosolic ATP concentration and fluorescent anti-ceramide antibodies to uncover ceramide formation. A 48 h exposure to chromium (VI) (≥10 μM) significantly increased cytosolic Ca(2+)-concentration, decreased ATP concentration (20 μM), decreased forward scatter, increased annexin V-binding and increased (albeit to a much smaller extent) hemolysis. Chromium (VI) did not significantly modify ceramide formation. The effect of 20 μM chromium (VI) on annexin V binding was partially reversed in the nominal absence of Ca(2+). The present observations disclose a novel effect of chromium (VI), i.e. Ca(2+) entry and cytosolic ATP depletion in erythrocytes, effects resulting in eryptosis with cell shrinkage and cell membrane scrambling.

Triggering of erythrocyte cell membrane scrambling by ursolic acid

Ursolic acid (1), a triterpenoid with pleotropic effects including inhibition of tumor growth, is well known to trigger apoptosis of nucleated cells. The effect is at least partially due to altered gene expression and mitochondrial dysfunction. Erythrocytes lack nuclei and mitochondria but, similar to nucleated cells, may undergo suicidal cell death or eryptosis, which is characterized by cell shrinkage and phospholipid scrambling of the cell membrane. Triggers of eryptosis include increase of cytosolic Ca2+ activity ([Ca2+]i), ceramide formation and/or ATP depletion. The present study has investigated whether or not 1 induces eryptosis. [Ca2+]i was estimated from Fluo-3 fluorescence, cell volume from forward scatter, phospholipid scrambling from annexin V binding, hemolysis from hemoglobin release, and cytosolic ATP concentration ([ATP]i) utilizing a luciferase assay and ceramide-utilizing fluorescent antibodies in FACS analysis. As a result, exposure of erythrocytes for 48 h to 1 (≥5 μM) did not significantly modify [ATP]i, but significantly increased [Ca2+]i, stimulated ceramide formation, decreased forward scatter, triggered annexin V binding, and elicited hemolysis. At 5 μM, 1 stimulated phospholipid scrambling in 10% and hemolysis in 2% of treated erythrocytes. Annexin V binding was blunted in the nominal absence of Ca2+. In conclusion, the food component ursolic acid stimulates suicidal death of erythrocytes, i.e., cells devoid of nuclei and mitochondria.

Stimulation of suicidal erythrocyte death by benzethonium

Benzethonium, an antimicrobial surfactant widely used as preservative of pharmaceuticals, topical wound care product and oral disinfectant, triggers apoptosis of several cell types. The apoptosis is preceded and possibly triggered by mitochondrial depolarization. Even though lacking mitochondria, erythrocytes may similarly undergo suicidal cell death or eryptosis. Hallmarks of eryptosis include cell shrinkage and cell membrane scrambling with phosphatidylserine exposure at the cell surface. Eryptosis may be triggered by energy depletion, which leads to increase of cytosolic Ca(2+)-activity with subsequent Ca(2+)-sensitive cell shrinkage and cell membrane scrambling. Ca(2+)-sensitivity is enhanced by ceramide. The present study explored the effect of benzethonium on eryptosis. Cell membrane scrambling was estimated from binding of fluorescent annexin V to phosphatidylserine, cell volume from forward scatter in FACS analysis, cytosolic Ca(2+)-concentration from Fluo3-fluorescence, hemolysis from hemoglobin release, lactate formation by colorimetry and ceramide utilizing fluorescent antibodies. A 48 hours exposure to benzethonium (=5μM) significantly increased cytosolic Ca(2+)-concentration, decreased forward scatter and triggered annexin V-binding affecting some 30% of the erythrocytes at 5 μM benzethonium. Only 5% of treated erythrocytes were hemolytic. The effects of benzethonium on annexin V binding were blunted in the nominal absence of Ca(2+) and in the presence of amiloride (1 mM) but not in the presence of the pancaspase inhibitor zVAD (10 μM). Benzethonium further significantly enhanced the effect of glucose depletion on cytosolic Ca(2+)-concentration and annexin V-binding, but significantly blunted the effect of glucose depletion on forward scatter. Benzethonium (5 μM) significantly enhanced lactic acid formation but not ceramide abundance. The present observations disclose a novel effect of benzethonium, i.e. triggering of suicidal death of erythrocytes.

Phlorhizin protects against erythrocyte cell membrane scrambling

Phlorhizin interferes with glucose transport. Glucose depletion triggers suicidal erythrocyte death or eryptosis, characterized by cell shrinkage and cell membrane scrambling. Eryptosis is further triggered by oxidative stress. The present study explored whether phlorhizin influences eryptosis following glucose depletion or oxidative stress. Cell membrane scrambling was estimated from annexin binding, cell volume from forward scatter (FSC), and cytosolic Ca(2+) concentration from Fluo-3 fluorescence. Phlorhizin (10-100 μM) added alone did not modify scrambling, FSC, or Fluo-3 fluorescence. Glucose depletion (48 h) significantly increased Fluo-3 fluorescence, decreased FSC, and increased annexin binding, effects in part significantly blunted by phlorhizin (annexin binding ≥ 10 μM, FSC ≥ 50 μM). Oxidative stress (30 min 0.3 mM tert-butylhydroperoxide) again significantly increased Fluo-3 fluorescence and triggered annexin binding, effects again in part significantly blunted by phlorhizin (Fluo-3 fluorescence ≥ 50 μM, annexin-binding ≥ 10 μM). Phlorhizin did not blunt the cell shrinkage induced by oxidative stress. The present observations disclose a novel effect of phlorhizin, that is, an influence on suicidal erythrocyte death following energy depletion and oxidative stress.

Stimulation of erythrocyte phospholipid scrambling by enniatin A

SCOPE

Enniatin A, a peptide antibiotic and common food contaminant, triggers mitochondrial dysfunction and apoptosis. Even though lacking mitochondria, erythrocytes may similarly undergo suicidal cell death or eryptosis. Eryptosis is characterized by cell shrinkage and cell membrane phospholipid scrambling. Triggers of phospholipid scrambling include energy depletion and increase in cytosolic Ca(2+) activity ([Ca(2+) ](i) ). The present study explored whether enniatin A triggers phospholipid scrambling.

METHODS AND RESULTS

Phospholipid scrambling was estimated from annexin-V-binding, cell volume from forward scatter (FSC), [Ca(2+) ](i) from Fluo3-fluorescence, cytosolic ATP-concentration ([ATP](i) ) using a luciferase assay and hemolysis from hemoglobin release. Exposure of erythrocytes for 48 h to enniatin A (≥ 2.5 μM) significantly increased [Ca(2+) ](i) , decreased [ATP](i) , decreased FSC, triggered annexin-V-binding and elicited hemolysis. Annexin-V-binding affected 25%, and hemolysis 2% of treated erythrocytes. Decreased [ATP](i) by glucose depletion for 48 h was similarly followed by increased [Ca(2+) ](i) , decreased FSC and annexin-V-binding. Enniatin A augmented the effect on [Ca(2+) ](i) and annexin-V-binding, but not on FSC. Annexin-V-binding was blunted by Ca(2+) removal, by the cation channel inhibitor amiloride (1 mM), by the protein kinase C inhibitor staurosporine (500 nM) but not by the pancaspase inhibitor zVAD (10 μM).

CONCLUSION

The food contaminant enniatin A triggers ATP depletion and increases cytosolic Ca(2+) activity, effects resulting in suicidal erythrocyte death.

Janus kinase 3 is expressed in erythrocytes, phosphorylated upon energy depletion and involved in the regulation of suicidal erythrocyte death

Janus kinase 3, a tyrosine kinase expressed in haematopoetic tissues, plays a decisive role in T-lymphocyte survival. JAK3 deficiency leads to (Severe) Combined Immunodeficiency (SCID) resulting from enhanced lymphocyte apoptosis. JAK3 is activated by phosphorylation. Nothing is known about expression of JAK3 in erythrocytes, which may undergo apoptosis-like cell death (eryptosis) characterized by cell membrane scrambling with phosphatidylserine exposure and cell shrinkage. Triggers of eryptosis include energy depletion. The present study utilized immunohistochemistry and confocal microscopy to test for JAK3 expression and phosphorylation, and FACS analysis to determine phosphatidylserine exposure (annexin binding) and cell volume (forward scatter). As a result, JAK3 was expressed in erythrocytes and phosphorylated following 24h and 48h glucose depletion. Forward scatter was slightly but significantly smaller in erythrocytes from JAK3-deficient mice (jak3(-/-)) than in erythrocytes from wild type mice (jak3(+/+)). Annexin V binding was similarly low in both genotypes. The JAK3 inhibitors WHI-P131/JANEX-1 (4-(4'-Hydroxyphenyl)amino-6,7-dimethoxyquinazoline, 156μM) and WHI-P154 (4-[(3'-Bromo-4'-hydroxyphenyl)amino]-6,7-dimethoxyquinazoline, 11.2μM) did not significantly modify annexin V binding or forward scatter. Glucose depletion increased annexin V binding, an effect significantly blunted in jak3(-/-) erythrocytes and in the presence of the JAK3 inhibitors. The observations disclose a completely novel role of Janus kinase 3, i.e. the triggering of cell membrane scrambling in energy depleted erythrocytes.

Inhibition of suicidal erythrocyte death by blebbistatin

Blebbistatin, a myosin II inhibitor, interferes with myosin-actin interaction and microtubule assembly. By influencing cytoskeletal dynamics blebbistatin counteracts apoptosis of several types of nucleated cells. Even though lacking nuclei and mitochondria, erythrocytes may undergo suicidal cell death or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine exposure at the cell surface. Triggers of eryptosis include energy depletion and osmotic shock, which enhance cytosolic Ca(2+) activity with subsequent Ca(2+)-sensitive cell shrinkage and cell membrane scrambling. The present study explored the effect of blebbistatin on eryptosis. Cell membrane scrambling was estimated from binding of annexin V to phosphatidylserine at the erythrocyte surface, cell volume from forward scatter in fluorescence-activated cell sorting analysis and cytosolic Ca(2+) concentration from Fluo3 fluorescence. Exposure to blebbistatin on its own (1-50 μM) did not significantly modify cytosolic Ca(2+) concentration, forward scatter, or annexin V binding. Glucose depletion (48 h) was followed by a significant increase of Fluo3 fluorescence and annexin V binding, effects significantly blunted by blebbistatin (Fluo3 fluorescence ≥ 25 μM, annexin V binding ≥ 10 μM). Osmotic shock (addition of 550 mM sucrose) again significantly increased Fluo3 fluorescence and annexin binding, effects again significantly blunted by blebbistatin (Fluo3 fluorescence ≥ 25 μM, annexin V binding ≥ 25 μM). The present observations disclose a novel effect of blebbistatin, i.e., an influence on Ca(2+) entry and suicidal erythrocyte death following energy depletion and osmotic shock.

Stimulation of suicidal erythrocyte death by oridonin

Oridonin triggers apoptosis of cancer cells and was suggested as anticancer agent. Oridonin is partially effective through mitochondrial depolarization and partially by modifying gene expression. Erythrocytes lack mitochondria and nuclei but may undergo eryptosis, a suicidal cell death characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine exposure at the cell surface. Triggers of eryptosis include increase of cytosolic Ca(2+)-activity, ATP depletion and ceramide formation. The present study explored, whether oridonin triggers eryptosis. Cytosolic Ca(2+)-concentration was estimated from Fluo3-fluorescence, cell volume from forward scatter in FACS analysis, phosphatidylserine exposure from binding of fluorescent annexin V, hemolysis from hemoglobin release, ATP concentration utilizing a luciferin-luciferase assay and ceramide abundance utilizing fluorescent anti-ceramide antibodies. A 48 h exposure to oridonin (≥25μM) significantly increased cytosolic Ca(2+)-concentration, increased ceramide formation, decreased forward scatter and triggered annexin V-binding (the latter in >20% of the erythrocytes). Oridonin didn't decrease ATP concentration and hemolysed <5% of erythrocytes. The effects of oridonin on annexin V binding were partially reversed in the nominal absence of Ca(2+) and by the addition of amiloride (1mM). The present observations reveal a completely novel effect of oridonin, i.e. triggering of Ca(2+) entry and ceramide formation as well as suicidal death of erythrocytes.

Beauvericin induced erythrocyte cell membrane scrambling

Beauvericin is a mycotoxin with antiviral, antibacterial, nematicidal, insecticidal, cytotoxic, and apoptotic activity. Similar to nucleated cells erythrocytes may undergo suicidal death or eryptosis, which is characterized by cell shrinkage and phosphatidylserine exposure at the erythrocyte surface. Eryptosis may be triggered by energy depletion leading to increase of cytosolic Ca²+ activity. The present study thus explored whether beauvericin is able to trigger eryptosis and influence eryptosis following energy depletion. Cell membrane scrambling was estimated from binding of annexin V to phosphatidylserine at the erythrocyte surface, cell volume from forward scatter in FACS analysis, cytosolic Ca²+ concentration from Fluo3 fluorescence, cytosolic ATP concentration from a luciferase-assay and ion channel activity with whole cell patch clamp. Exposure to beauvericin (≥ 5 μM) significantly decreased erythrocyte ATP concentration and increased cytosolic Ca²+ concentration as well as annexin V-binding. The effect of beauvericin on annexin V binding was significantly blunted by removal of extracellular Ca²+. Glucose depletion (48 h) was followed by, increase of Fluo3 fluorescence, decrease of forward scatter and increase of annexin V-binding. Beauvericin (≥ 1 μM) augmented the effect of glucose withdrawal on Fluo3 fluorescence and annexin V-binding, but significantly blunted the effect of glucose withdrawal on forward scatter, an effect paralleled by inhibition of Ca²+ activated K+ channels. The present observations disclose novel effects of beauvericin, i.e. stimulation of Ca²+ entry with subsequent cell membrane scrambling and inhibition of Ca²+ activated K+ channels with blunting of cell shrinkage.

Stimulation of suicidal erythrocyte death by α-lipoic acid

α-lipoic acid, a nutrient with both, antioxidant and oxidant activity induces apoptosis in a variety of cells. Owing to its proapoptotic potency α-lipoic acid has been suggested for the therapy of cancer. α-Lipoic acid stimulates apoptosis by induction of oxidative stress and subsequent activation of caspases. Oxidative stress could similarly trigger caspase activation and suicidal erythrocyte death or eryptosis, which is characterized by cell membrane scrambling and cell shrinkage. Eryptosis is triggered by increase of cytosolic Ca(2+) concentration and/or ceramide formation. The present study explored whether α -lipoic acid influences eryptosis. Cell membrane scrambling was estimated from binding of annexin V to phosphatidylserine at the erythrocyte surface, cell volume from forward scatter in FACS analysis, cytosolic Ca(2+) concentration from Fluo3 fluorescence, caspase activation and ceramide formation utilizing respective antibodies, cytosolic ATP concentration from a luciferase-assay. Within 48 hours, exposure to α-lipoic acid (10 - 75 mM) significantly decreased forward scatter, increased cytosolic Ca(2+) concentration, decreased ATP concentration, activated caspase 3, stimulated formation of ceramide and triggered annexin V-binding. Glucose depletion (48 h) was followed by decrease of forward scatter and increase of annexin V-binding, effects significantly augmented in the presence of α-lipoic acid (20 mM). Oxidative stress (30 min 0.3 mM tert-butylhydroperoxide) similarly triggered annexin binding, an effect slightly but significantly blunted by α-lipoic acid. In conclusion, α-lipoic acid triggers eryptosis but by the same token counteracts eryptosis during oxidative stress. α-lipoic acid sensitive eryptosis may lead to anemia and derangements of microcirculation.